Apparatus for detecting abnormality in speed changing system

ABSTRACT

An object of this invention consists in exactly specifically identifying the position where abnormality arises in a speed changing system installed on a construction machine or similar vehicle. Specifically, a microprocessor (29) determines whether or not clutches H and L and clutch R, 1st, 2nd, 3rd and 4th are brought in an engaged state in conformity with clutch pressure commands (C 1  l to C 7 ). In addition, the microprocessor (29) determines whether or not the clutches are selected and then brought in an engaged state in conformity with the clutch pressure commands and shafts (2a, 7a and 8a) located before and behind the clutches are rotated in conformity with speed reduction ratios corresponding to the selected clutches. Thereafter, the microprocessor (29) exactly specifically identifies based on the results derived from the aforementioned determinations the position where a failure arises in the speed changing system. In other words, the microprocessor (29) determines whether the failure arises in an electrical system (sensors 9, 11 and 19 to 20) or in a mechanical system (clutch valves 12, 13 and 14 to 18). The apparatus of the present invention is preferably used by installing it on a vehicle such as a construction machine or the like.

TECHNICAL FIELD

The present invention relates to an apparatus for detecting abnormalitywhich arises at a certain position in a speed changing system for amovement machine, a construction machine or the like.

BACKGROUND ART

FIG. 6 is a block diagram which schematically illustrates by way ofexample the structure of a conventional apparatus for detectingabnormality in a speed changing system.

As shown in the drawing, an output from an engine 41 is transmitted to atransmission 43 via a torque converter 42, and an output from thetransmission 43 is then transmitted to driving wheels 44 via adifferential gear unit and a speed reducing unit at a final stage bothof which are not shown in the drawing.

The engine 41 is equipped with an engine rotation sensor 45 from which asignal is inputted into a controller 46 corresponding to the presentrotational speed of the engine 41. In addition, each of the drivingwheels 44 is equipped with a vehicle speed sensor 47 from which a signalis also inputted into the controller 46 corresponding to the presentvehicle speed.

Subsequently, the controller 46 outputs a speed stage command to obtaina speed stage in conformity with the speed stage command so as toactuate a transmission clutch shift valve 48, causing a certain speedchanging clutch in the transmission 43 to be selected and then broughtin an engaged state.

Conventionally, the speed changing system is provided with anabnormality detecting apparatus for detecting abnormality of each of theengine rotation sensor 45 and the vehicle speed sensor 47 in response tooutputs from these sensors 45 and 47.

This abnormality detecting apparatus is intended to detect theabnormality based on the result derived from comparison of an outputfrom the engine rotation sensor 45 with an output from the vehicle speedsensor 47. For example, in a case where the present speed stage remainsat a certain speed stage other than a neutral stage, the abnormalitydetecting apparatus determines whether an output from the enginerotation sensor 45 exceeds a threshold of 2500 r.p.m. or not, andmoreover, determines whether an output from the vehicle speed sensor 47is reduced to a level of zero kilometer or not. At this time, as shownin FIG. 7, when it is found that the output from the engine rotationsensor 45 exceeds the threshold of 2500 r.p.m. and the output from thevehicle speed sensor 47 is reduced to a level of zero kilometer, theabnormality detecting apparatus determines that "abnormality is presentwith respect to the vehicle speed sensor 47" (which represents that avehicle speed signal system is abnormal).

Since the conventional abnormality detecting apparatus is constructed inthe above-described manner, it makes the aforementioned determination onthe assumption that the transmission clutch shift valve 48 is properlyactuated and the speed changing clutch is properly brought in an engagedstate.

When it is confirmed that the transmission clutch shifting valve 48 isproperly actuated and the speed changing clutch is properly brought inan engaged state, it can be concluded that the aforementioneddetermination has been made correctly. However, in a case where thevehicle speed sensor 47 operates correctly but abnormality arises in ahydraulic system, there may be caused an occasion that an output fromthe engine rotation sensor 45 exceeds 2500 r.p.m. and an output from thevehicle speed sensor 47 is reduced to a level of zero kilometer evenwhen the transmission clutch shift valve 48 fails to operate properlyand the present speed changing stage in the transmission 43 remainsstill at a neutral stage. Also in this case, the abnormality detectingapparatus determines that "abnormality is present with respect to thevehicle sensor 47". This means that the abnormality detecting apparatusfails to exactly detects the practical position where the abnormalityhas arisen.

As is apparent from the above description, the conventional abnormalitydetecting apparatus has a problem that it is short of reliability, sinceit can not specifically identify the practical position where theabnormality has arisen.

The present invention has been made in consideration of the foregoingbackground and its object resides in providing an apparatus fordetecting abnormality in a speed changing system wherein the apparatusassures that the position where abnormality arises in the speed changingsystem can specifically be identified with excellent accuracy.

DISCLOSURE OF THE INVENTION

According to the present invention, there is provided an apparatus fordetecting abnormality in a speed changing system including atransmission composed of a plurality of speed changing clutches toperform a speed changing operation in response to a speed stage commandso as to select one of the speed changing clutches and then bring it inan engaged state, wherein the apparatus comprises clutch engaged statedetecting means arranged independently of the speed changing clutches todetect whether the speed changing clutch is brought in an engaged stateor not; rotational speed detecting means for detecting a rotationalspeed of each of shafts located before and behind the speed changingclutches; clutch engaged state determining means for determining basedon the content of the speed stage command in response to an output fromthe clutch engaged state detecting means with respect to each of thespeed changing clutches whether or not the speed changing clutch isbrought in an engaged state in conformity with the content of the speedstage command; rotational speed determining means for determining basedon the content of the speed stage command in response to an output fromthe rotational speed detecting means whether or not one of the shaftslocated before and behind the speed changing clutches is rotated at aspeed reduction ratio corresponding to the speed changing clutch whichhas been selected and then brought in an engaged state in conformitywith the content of the speed stage command; and means for detectingbased on the results derived from the determinations of the clutchengaged state determining means and the rotational speed determiningmeans the position where the abnormality has arisen in the speedchanging system.

With such construction as defined above, the practical position wherethe abnormality has arisen in the speed changing system of the apparatuscan exactly be detected by combining the result derived from thedetermination of the clutch engaged state determining means with theresults derived from the determination of the rotational speeddetermining means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram which schematically illustrates the structureof an apparatus for detecting abnormality in a speed changing system inaccordance with an embodiment of the present invention, FIG. 2 is aflowchart which schematically illustrates a series of processings to beexecuted by the apparatus in accordance with a failure diagnosisroutine, FIG. 3 is a flowchart which schematically illustrate anotherseries of processings to be executed further by the apparatus inaccordance with the diagnosis routine shown in FIG. 3, FIG. 4(a) andFIG. 4(b) are illustrative views which show determinations to be made bya controller in the apparatus, respectively, FIG. 5(a), FIG. 5(b) andFIG. 5(c) are another illustrative views which show determinations to bemade by the controller in the apparatus, respectively, FIG. 6 is a blockdiagram which schematically illustrates the structure of a conventionalapparatus for detecting abnormality in a speed changing system, and FIG.7 is an illustrative view which shows determination to be executed by acontroller in the conventional apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in detail hereinafter withreference to the accompanying drawings which illustrate a preferredembodiment of the present invention.

FIG. 1 is a block diagram which schematically illustrates the structureof an apparatus for detecting abnormality in a speed changing system inaccordance with the embodiment of the present invention.

Referring to FIG. 1, an output from an engine 1 is transmitted to atransmission 3 via a converter 2, and an output from the transmission 3is then transmitted to driving wheels 4 via a differential gear unit anda speed reducing unit at a final stage both of which are not shown inthe drawing.

The engine 1 is equipped with an engine speed sensor 5 adapted to outputa signal corresponding to an engine speed NE so that an output from theengine speed sensor 5 is inputted into a controller 6.

A speed changing command indicative of a speed stage to be assumed bythe transmission 3 is inputted into the controller 6 from a shiftselector which is not shown in the drawing.

The transmission 3 is essentially composed of an auxiliary speedchanging unit 7 including speed changing clutchs H and L at a firststage (hereinafter referred to simply as H/L clutches) operativelyconnected to an output shaft 2a of the torque converter 2 (hereinafterreferred to simply as a transmission input shaft) and a main speedchanging unit 8 including a speed changing clutch R (clutch for rearwardmovement) and first to fourth clutches 1st, 2nd, 3rd and 4th(hereinafter referred to simply as SP clutches) at a second stageoperatively connected to an output shaft 7a of the auxiliary speedchanging unit 7 (hereinafter referred to simply as a transmissionintermediate shaft) so as to selectively determine a speed stage bycombination of one of the H/L clutches on the auxiliary speed changingunit 7 side with one of the SP clutches on the main speed changing unit8 side.

The transmission input shaft 2a is equipped with a transmission inputshaft rotation sensor 9 for detecting a rotational speed N_(IN) thereof,the transmission intermediate shaft 7a is equipped with a transmissionintermediate shaft rotation sensor 10 for detecting a rotational speedN_(MID) thereof, and an output shaft 8a of the main speed changing unit8 (hereinafter referred to simply as a transmission output shaft) isequipped with a transmission output shaft rotation sensor 11 fordetecting a rotational speed N_(OUT) thereof so that the detected valueN_(IN) of the sensor 9, the detected value N_(MID) of the sensor 10 andthe detected value N_(OUT) of the sensor 10 are inputted into thecontroller 6.

H/L clutch valves 12 and 13 each adapted to be actuated in response toan electric signal are separately hydraulically connected to the H/Lclutches H and L so that the H/L clutches H and L are hydraulicallycontrolled by the H/L clutch valves 12 and 13 hydraulically connectedthereto.

Similarly, SP clutch valves 4 to 18 each adapted to be actuated inresponse to an electric signal are separately hydraulically connected tothe SP clutches R, 1st, 2nd, 3rd and 4th so that the SP clutche R isseparately controlled by the SP clutch valves 14 to 18 hydraulicallyconnected thereto.

Each of the H/L clutch valves 12 and 13 and the SP clutch valves 14 to18 includes a proportional solenoid (not shown) which serves as anactuator for displacing each spool so as to enable a hydraulic pressureto be generated in proportion to an intensity of driving electriccurrent inputted into each proportional solenoid. The H/L clutch valves12 and 13 and the SP clutch valves 14 to 18 are supplied withpressurized hydraulic oil from a hydraulic pump (not shown) via a mainrelief valve (not shown).

Clutch pressure command signals are inputted into the H/L clutch valves12 and 13 and the SP clutch valves 14 to 18 from the controller 6 via adrive circuit (not shown) in order to shift desired clutches of the H/Lclutches and the SP clutches to ON (engagement) or shift them to OFF(disengagement). Specifically, after clutch pressure command signals C₁,C₂ and C₃ to C₇ outputted from the controller 6 are amplified in thedrive circuit, they are inputted into the H/L clutch valves 12 and 13and the SP clutch valves 14 to 18. Thus, the foregoing clutch pressurecommand signals and an intensity of electric current flowing througheach of the aforementioned solenoids are kept in the proportionalrelationship relative to each other.

In addition, the H/L clutches H and L are equipped with clutch pressuresensors 19 and 20 for detecting each clutch pressure exerted thereon,while the SP clutches R, 1st, 2nd, 3rd and 4th are equipped with clutchpressure sensors 21 to 25 for detecting each clutch pressure exertedthereon. The clutch pressure sensors 19, 20 and 21 to 25 are actuatedsuch that they are turned on when the active clutch pressure is higherthan a preset value (value substantially equal to 1/2 of a clutch setpressure), while they are turned off when the active clutch pressure islower than the preset value. Signals S₁ and S₂ representing that theclutch pressure sensors 19 and 20 are turned on or off as well assignals S₃ to S₇ representing that the clutch pressure sensors 21 to 25are turned on or off are inputted into the controller 6.

It should be noted that the aforementioned preset pressure is athreshold for determining whether the H/L clutches and the SP clutchesare brought in an engaged state or released from the engaged state. Asshown in FIG. 1, the controller 6 is essentially composed of an inputcircuit 26 into which the detection signals S₁ and S₂ of the clutchpressure sensors 19 and 20, the detection signals S₃ to S₇ of the clutchpressure sensors 21 to 25, the detection signal NE of the enginerotation sensor 5, the detection signal N_(IN) of the transmission inputshaft rotation sensor 9, the detection signal N_(MID) of thetransmission intermediate shaft rotation sensor 10 and the detectionsignal N_(OUT) of the transmission output shaft rotation sensor 11 areinputted, a ROM 27 in which a flowchart for executing the content ofitems shown in Table 1 to Table 4 to be described later as well as aseries of speed changing processings to be described later and aflowchart shown in FIG. 2 and FIG. 3 are memorized, a RAM 28 in whichcalculation equations (to be described later) required for executing aseries of processings in accordance with the aforementioned flowchartsare memorized, a microprocessor 29 for executing the content of eachflowchart based on the content of items memorized in the ROM 27 and theRAM 28 in response to the signals S₁, S₂, S₃ to S₇, NE, N_(IN), N_(MID)and N_(OUT), and an output circuit 30 from which the clutch pressurecommand signals C₁, C₂, C₃ to C₇ are outputted to the H/L clutch valves12 and 13 and the SP clutch valves 14 to 18 based on the results derivedfrom a series of processings executed in the microprocessor 29.

Table 1 shows a relationship between the speed stages R, N (neutral), F₁to F₇ selected by the shift selector and combination of the H/L clutcheswith the SP clutches corresponding to the selected speed stage.

                  TABLE 1                                                         ______________________________________                                        speed stage    H/L clutch                                                                              SP clutch                                            ______________________________________                                        R              L         R                                                    F.sub.1        L         1st                                                  F.sub.2        L         2nd                                                  F.sub.3        H         2nd                                                  F.sub.4        L         3rd                                                  F.sub.5        H         3rd                                                  F.sub.6        L         4th                                                  F.sub.7        H         4th                                                  ______________________________________                                    

The microprocessor 29 executes a certain speed changing processing basedon the content of items shown in Table 1.

For example, when it is assumed that the speed stage command F₁ (firstspeed for forward movement) is inputted into the controller 6 by theshift selector, the H/L clutch L and the SP clutch 1st are selected,whereby an ON signal for bringing the H/L clutch L in an engaged state(which represents that the content of the clutch pressure command signalC₂ is ON) and an ON signal for bringing the SP clutch 1st in an engagedstate (which represents that the content of the clutch pressure commandsignal C₃ is ON) are outputted from the output circuit 30, and moreover,an OFF signal for releasing all the remaining clutches from the engagedstate (which represents that the content of each of the clutch pressurecommand signals C₁ and C₄ to C₇ is OFF) is outputted from the outputcircuit 30.

In a case where it is found that the H/L clutch valves 12 and 13 and theSP clutch valves 14 to 18 are correctly actuated in conformity with thecontent of the clutch pressure command signals C₁ to C₇, the H/L clutchL and the SP clutch 1st are brought in an engaged state and otherclutches are released from the engaged state, resulting in correct speedchanging (speed changing in conformity with the content shown inTable 1) being achieved. However, in a case where abnormality arises inthe hydraulic system for actuating the respective clutches, there may becaused an occasion that speed changing fails to be achieved correctly.In addition, there may be caused an occasion that abnormality ariseswith the rotation sensors 9, 10 and 11 arranged corresponding to therespective shafts in the transmission 3 in which a speed changingoperation is performed, resulting in correct detection failing to becarried out by the rotation sensors 9, 10 and 11. Additionally, theremay be caused an occasion that abnormality arises with the clutchpressure sensors 19 and 20 and the clutch pressure sensors 21 to 25,resulting in correct detection failing to be carried out by therespective sensors 19 to 25.

In presumptive consideration of the aforementioned occasions, themicroprocessor 29 executes a failure diagnosis routine for exactlyspecifically identifying the position where abnormality arises (positionwhere a failure arises), as an interruption processing associated withthe aforementioned speed changing processing.

Specifically, when a series of processings to be executed in accordancewith the aforementioned failure diagnosis routine as shown in FIG. 2 arestarted, the controller 6 determines based on the output NE from theengine rotation sensor 5 whether or not the engine is rotated and thehydraulic pump is actuated, in consideration of the result derived fromthe determination as to whether the engine speed NE exceeds apredetermined engine speed NES or not (step 101).

In a case where the result derived from the determination at the step101 is NO, in other words, in a case where it is found that the enginespeed NE is lower than the predetermined engine speed NES, the programgoes to a step 116 (see FIG. 3) without any execution of subsequentprocessings (failure diagnosis processings). At the step 116, thecontroller 6 executes another routine different from a series of failurediagnosis processings.

In a case where the result derived from the determination at the step101 is YES, in other words, in a case where it is found that the enginespeed NE exceeds the predetermined engine speed NES, the controller 6executes a series of failure diagnosis processings.

First, the controller 6 successively compares the content of therespective clutch pressure command signals C₁ to C₇ presently outputtedfrom the output circuit 30 during the aforementioned speed changingprocessing with the content of the respective detection signals S₁ to S₇of the clutch pressure sensors 19 to 25, with respect to each of theclutches H, L, R, 1st, 2nd, 3rd and 4th. Then, the controller 6determines based on the results derived from the foregoing comparisonwhether the H/L clutches H and L and the SP clutches R, 1st, 2nd, 3rdand 4th are brought in an engaged state or released from the engagedstate in conformity with the content representative of the command ofthe clutch pressure command signals C₁ to C₇. Concretely, in a casewhere it is found that the content representative of the respectiveclutch pressure command signals C₁ to C₇ is ON, the controller 6executes a processing for determining whether or not the contentrepresentative of the detection signals S₁ to S₇ is ON in conformitywith the ON command with respect to each of the clutches H, L, R, 1st,2nd, 3rd and 4th (step 103). In addition, in a case where it is foundthat the content representative of the respective clutch pressurecommand signals C₁ to C₇ is OFF, the controller 6 executes a processingfor determining whether or not the content representative of therespective detection signals S₁ to S₇ of the clutch pressure sensors 19to 25 is OFF in conformity with the OFF command with respect to each ofthe clutches H, L, R, 1st, 2nd, 3rd and 4th (step 104).

In a case where it is found that the practical clutch pressure is OFF inresponse to a clutch pressure ON command, the controller 6 determinesthat "the clutch pressure ON command is not coincident to the practicalclutch pressure" (which represents that the result derived from thedetermination at the step 103 is YES (see FIG. 4(a)). Then, the contentof specific identification of the clutch for which the foregoingdetermination has been made is stored in the RAM 28 in such a mannerthat e.g., "the clutch pressure ON signal is not coincident to thepractical clutch pressure with respect to the H/L clutch L" (step 109).Similarly, in a case where it is found that the practical clutchpressure is ON in response to a clutch pressure OFF command, thecontroller 6 determines that "the clutch pressure OFF command is notcoincident to the practical clutch pressure" (which represents that theresult derived from the determination at the step 104 is YES (see FIG.4(b)). Then, the content of specific identification of the clutch forwhich the foregoing determination has been made is memorized in the RAM28 in such a manner that e.g., "the clutch pressure OFF command is notcoincident to the practical clutch pressure with respect to the H/Lclutch H" (step 110).

On the other hand, in a case where it is found that the practical clutchpressure is ON in response to a clutch ON command (which represents thatthe result derived from the determination at the step 103 is NO), andmoreover, the practical clutch pressure is OFF in response to a clutchpressure OFF command is OFF (which represents that the result derivedfrom the determination at the step 104 is NO) the controller 6determines that the content representative of the commands of the clutchpressure command signals C₁ to C₇ is "coincident" to the practicalengaged/disengaged state of each of the H/L clutches H and L and the SPclutches R, 1st, 2nd, 3rd and 4th.

At subsequent steps 105 and 106, the controller 6 determines, based onthe content representative of the commands of the clutch pressurecommand signals C₁ to C₇ presently outputted from the output circuit 30during the aforementioned speed changing processing, the output N_(IN)from the transmission input shaft rotation sensor 9, the output N_(MID)from the transmission intermediate shaft sensor 10 and the outputN_(OUT) from the transmission output shaft rotation sensor 11, whetheror not the respective shafts 2a, 7a and 8a are rotated in conformitywith the content representative of the respective commands of the clutchpressure command signals C₁ to C₇.

Table 2 shows a relationship between the H/L clutches H and L and aspeed reduction ratio G_(HL) of the auxiliary speed reduction unit 7 atthe time when the H/L clutches are brought in an engaged state, andTable 3 shows a relationship between the SP clutches R, 1st, 2nd, 3rdand 4th and a speed reduction ratio G_(SP) of the main speed reductionunit 8 at the time when the SP clutches R, 1st, 2nd, 3rd and 4th arebrought in an engaged state.

                  TABLE 2                                                         ______________________________________                                               H/L clutch                                                                            G.sub.HL                                                       ______________________________________                                               L       1.00                                                                  H       0.74                                                           ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                                SP clutch                                                                            G.sub.SP                                                       ______________________________________                                                R      0.39                                                                   1st    4.69                                                                   2nd    3.33                                                                   3rd    1.82                                                                   4th    1.00                                                           ______________________________________                                    

The controller 7 can determine whether or not the respective shafts 2a,7a and 8a are rotated in conformity with the content representative ofthe clutch command signals C₁ to C₇, depending on the determination withrespect to whether or not the respective shafts 2a, 7a and 8a arerotated in conformity with the speed reduction ratios corresponding tothe H/L clutches and the SP clutches each of which engaged state isindicated in response to each of the clutch pressure command signals C₁to C₇.

Then, the controller 7 reads from Table 2 the speed reduction ratioG_(HL) of one of the H/L clutches of which content representative ofeither of the clutch pressure command signals C₁ and C₂ is ON, andthereafter, calculates a rotational speed deviation ΔHL appearing in theauxiliary speed reduction unit 7 in accordance with the followingequation.

    ΔH L=|N IN-N MID×G HL|       (1)

In addition, the controller 6 reads from Table 3 the speed reductionratio G_(SP) of one of the SP clutches of which content representativeof one of the clutch pressure command signals C₃ to C₇ is ON, andthereafter, calculates a rotational deviation ΔSP appearing in the mainspeed changing unit 8 in accordance with the following equation.

    ΔS P=|N MID-N OUT×G SP|      (2)

Additionally, the controller 6 calculates a rotational speed deviationΔT/M appearing in the transmission 3 based on the speed reduction ratiosG_(HL) and G_(SP) in accordance with the following equation.

    ΔT/M=|N IN-N OUT×G HL×G SP| (3)

Subsequently, the controller 6 determines whether each of the rotationalspeed deviations ΔHL, ΔSP and ΔT/M exceeds a threshold N_(s) or not.This threshold N_(s) is used as a threshold with which determination ismade as to whether or not the input shaft 2a and the output shaft 7a ofthe auxiliary speed changing unit 7 are rotated in conformity with theaforementioned speed reduction ratio G_(HL) or whether or not the inputshaft 7a and the output shaft 8a of the main speed changing unit 8 arerotated in conformity with the aforementioned speed reduction ratioG_(SP) or whether or not the input shaft 2a and the output shaft 8a ofthe transmission 3 are rotated in conformity with the aforementionedspeed changing ratio G_(HL)×G_(SP). In practice, the threshold N_(S) ispredetermined in consideration of the performances of the transmission 3and other factors. It should be noted that the threshold N_(S) may bevaried in dependence on each of the rotational speed deviations ΔHS, ΔSPand ΔT/M.

After the three kinds of determinations have been made in theabove-described manner, the controller 6 makes another determinationbased on the results derived from the aforementioned determinations withrespect to items as shown in FIG. 5(a) to FIG. 5(c).

In detail, as shown in FIG. 5(a), in a case where the rotational speeddeviations ΔT/M and ΔHL are equal to or more than the threshold N_(S)and the rotational speed deviation ΔSP is less than the threshold N_(S),the controller 6 can determine that the input shaft 2a and the outputshaft 7a of the auxiliary speed changing unit 7 are rotated inconformity with the speed reduction ratio G_(HL) but the input shaft 7aand the output shaft 8a of the main speed changing unit 8 are notrotated in conformity with the speed reduction ratio G_(SP). At thistime, the content of the foregoing determination representing theaforementioned fact, i.e., "abnormality is present with respect to therotational speed deviation ΔHL" is memorized in the RAM 28 (whichrepresents that the result derived from the determination at the step107 is YES, step 111).

In addition, as shown in FIG. 5(b), in a case where the rotational speeddeviations ΔT/M and ΔSP are equal to or more than the threshold N_(S)and the rotational speed deviation ΔHL is less than the threshold N_(S),the controller 6 can determine that the input shaft 2a and the outputshaft 7a of the the auxiliary speed changing unit 7 are rotated inconformity with the speed reduction ratio G_(HL) but the input shaft 7aand the output shaft 8a of the main speed are not rotated in conformitywith the speed reduction ratio G_(SP). At this time, the content of theforegoing determination representing the aforementioned fact, i.e.,"abnormality is present with respect to the rotational speed deviationΔSP" is memorized in the RAM 28 (which represents that the resultderived from the determination at the step S108 is YES, step 112).Additionally, as shown in FIG. 5(c), in a case where the rotationalspeed deviations ΔHL and ΔSP are equal to or more than the thresholdN.sub. S and the rotational speed deviation ΔT/M is less than thethreshold N_(S), the controller 6 can determine that the input shaft 2aand the output shaft 8a of the transmission 3 are rotated in conformitywith the speed reduction ratio G_(HL) ×G_(SP) and the rotational speedN_(MIN) of the intermediate shaft 7a is abnormal. In other words, thecontroller 6 can determine that there occurs such a failure thatabnormality arises with respect to the intermediate shaft rotationsensor 10. In this case, since there does not appears any trouble withrespect to running of the engine, the controller 6 operates such thatthe present speed stage is held while the content of the present clutchpressure command signal outputted from the output circuit 30 isunchangeably maintained (step 106).

When the program goes to a step 113, the controller 6 makesdetermination with respect to the failure position in accordance with afailure position determining table shown in Table 4 with reference tothe content of the following items memorized in the controller 6, one ofthem being an item which represents that "clutch pressure ON commandsare not coincident to the practical clutch pressure", other one of thembeing an item which represents that clutch pressure OFF commands are notcoincident to the practical clutch pressure", another one being an itemwhich represents that "abnormality is present with respect to therotational speed deviation ΔHL" and further another one of them being anitem which represents that "abnormality is present with respect to therotational speed deviation ΔSP".

                                      TABLE 4                                     __________________________________________________________________________                    Rotation signal system                                                        HL abnormal     SP abnormal                                                   Present Absent  Present Absent                                __________________________________________________________________________    Clutch                                                                             H/L  Coinci-                                                                             (1)Abnormal-                                                                          (2)Normal                                             pressure                                                                           clutches                                                                           dence ity in                                                        signal          input                                                         system          shaft                                                                         rotation                                                                      sensor                                                                        system                                                                        (Electric-                                                                    al system)                                                              ON non-                                                                             (3)Abnormal-                                                                          (4)Abnormal-                                                    coinci-                                                                             ity 1 in                                                                              ity in                                                          dence HL clutch                                                                             Pressure                                                              valves  sensor                                                                (Hydraulic                                                                            system                                                                system) (Electrical                                                                   system)                                                         OFF non-                                                                            (5)Abnormal-                                                                          (6)Abnormal-                                                    coinci-                                                                             ity 2 in                                                                              ity in                                                          dence HL clutch                                                                             pressure                                                              valves  sensor                                                                (Hydraulic                                                                            system                                                                system) (Electrical                                                                   system)                                                    SP   Coinci-               (7)Abnormal-                                                                          (8)Normal                                  clutches                                                                           dence                 ity in                                                                        output                                                                        shaft                                                                         sensor                                                                        system                                                                        (Electrical                                                                   system)                                                 ON non-               (9)Abnormal-                                                                          (10)Abnormal-                                   coinci-               ity 1 in                                                                              ity in                                          dence                 SP clutch                                                                             pressure                                                              valves  sensor                                                                (Hydraulic                                                                            system                                                                system) (Electrical                                                                   system)                                         OFF non-              (11)Abnormal-                                                                         (12)Abnormal-                                   coinci-               ity 2 in                                                                              ity in                                          dence                 SP clutch                                                                             pressure                                                              valves  sensor                                                                (Hydraulic                                                                            system                                                                system) (Electrical                                                                   system)                               __________________________________________________________________________

Specifically, as is apparent from Table 4, the controller 6 makesdetermination in the following manner.

(1) In a case where the content of clutch pressure command signals withrespect to the H/L clutches is "coincident" to the practically engagedstate of each of the H/L clutches, and moreover, in a case where"abnormality is present with respect to the rotational speed deviationΔHL", since it is considered that there occurs such a malfunction that"abnormality is present with respect to the rotational speed deviationΔHL" merely due to an occurrence of abnormality of the input shaftrotation sensor 9 although the H/L clutches are brought in a normallyengaged state, the controller 6 determines that there occurs such afailure that "abnormality arises with the input shaft rotation sensor9".

(2) In a case where there is "coincidence" with respect to each of theH/L clutches, and moreover, in a case where the rotational speeddeviation ΔHL is not abnormal, since there does not appear any problem,the controller 6 determines that the H/L clutches are "normal".

(3) In a case where "clutch pressure ON commands are not coincident tothe practical clutch pressure" with respect to the H/L clutches and"abnormality is present with respect to the rotational speed deviationΔHL", since it is considered that "abnormality is present with respectto the rotational speed deviation ΔHL" because the H/L clutches are notbrought in a normally engaged state, the controller 6 determines thatthere occurs such a failure that "abnormality arises with respect toeach of the H/L clutch valves 12 and 13".

(4) In a case where "clutch pressure ON commands are not coincident tothe practical clutch pressure with respect to the H/L clutches" and therotational speed deviation ΔHL is not abnormal, since it is consideredthat "clutch pressure ON commands are not coincident to the practicalclutch pressure" because outputs S₁ and S₂ from the clutch pressuresensors 19 and 20 are abnormal, the controller 6 determines that thereoccurs such a failure that abnormality arises with each of the clutchpressure sensors 19 and 20".

(5) In a case where "clutch pressure OFF commands are not coincident tothe practical clutch pressure" with respect to the H/L clutches and"abnormality is present with respect to the rotational speed abnormalityΔHL", since it is considered that "abnormality is present with respectto the H/L clutches" because the H/L clutches are not released fromtheir engaged state, the controller 6 determines that there occurs sucha failure that "abnormality arises with each of the H/L clutch valves 12and 13".

(6) In a case where "clutch pressure OFF commands are not coincident tothe practical clutch pressure" with respect to the H/L clutches and therotational speed deviation ΔHL is not abnormal, since it is consideredthat "clutch pressure OFF commands are not coincident to the practicalclutch pressure" because outputs S₁ and S₂ from the clutch pressuresensors 19 and 20 are abnormal, the controller 6 determines that thereoccurs such a failure that "abnormality arises with each of the clutchpressure sensors 19 and 20".

Next, with respect to the SP clutches, the controller makesdetermination in the following manner.

(7) In a case where there is "coincidence" with respect to the SPclutches and "abnormality is present with respect to the rotationalspeed deviation ΔSP", the controller 6 determines that there occurs sucha failure that "abnormality arises with the output shaft rotation sensor11".

(8) In a case where "there is "coincidence" with respect to the SPclutch 4 and the rotational speed deviation ΔSP is not abnormality, thecontroller 6 determines that all is "normal".

(9) In a case where "clutch pressure ON commands are not coincident tothe practical clutch pressure" and "abnormality is present with respectto the rotational speed deviation ΔSP", the controller 6 determines thatthere occurs such a failure that "abnormality arises with the SP clutchvalves 14 to 18".

(10) In a case where "clutch pressure ON commands are not coincident tothe practical clutch pressure" and the rotational speed deviation ΔSP isnot abnormal, the controller 6 determines that there occurs such afailure that "abnormality arises with the clutch pressure sensors 21 to25".

(11) In a case where "clutch pressure OFF commands are not coincident tothe practical clutch pressure" and "abnormality is present with respectto the rotational speed deviation ΔSP", the controller 6 determinesthere occurs such a failure that abnormality arises with the SP clutches14 to 18".

(12) In a case where "clutch pressure OFF commands are not coincident tothe practical clutch pressure" and the rotational speed deviation ΔSP isnot abnormal, the controller 6 determines that "abnormality arises withthe clutch pressure sensors 21 to 26".

As described above, with respect to the paragraphs (1) to (12), thecontroller 6 determines that there occurs some failure (or thecontroller 6 determines that all is normal) (step 113).

Next, in a case where the controller 6 determines that abnormality ispresent with respect to the H/L clutches valves 12 and 13, the clutchpressure sensors 19 and 20, the SP clutch valves 14 to 18 or the clutchpressure sensors 21 to 25 as mentioned above in the paragraphs (3), (4),(5), (6), (9), (10), (11) and (12), the controller 6 specificallyidentifies the position where a failure has arisen, based on the resultsderived from the determinations and the content of clutch pressurecommand signals C₁ to C₇ which are combined with each other.

For example, in a case where a clutch pressure command signal isoutputted so as to allow the SP clutch R is brought in an engaged state(which represents that the content of the clutch pressure command signalC₃ is "ON"), and moreover, the controller 6 determines that a failurearises as described in the paragraph (9), the controller 6 specificallyidentifies the failure position such that the SP clutch valve 14corresponding to the SP clutch R fails to operate properly (step 114).

Next, the controller 6 executes one of the following processingscorresponding to the failure position based on the result derived fromthe determination on the failure position at the step 113 and the resultderived from the specific identification of the failure position at thestep 114.

(1) In a case where the controller 6 determines that there arises such afailure that abnormality is present with respect to the H/L clutchvalves 12 and 13 or the SP clutch valves 14 to 18 (corresponding to thedeterminations as described in the paragraphs (3), (5), (9) and (11)),and moreover, the controller 6 specifically identifies the failureposition, since it is inhibitive from the viewpoint of safety thatrunning of the engine continues further while the presently selectedspeed stage is unchangeably maintained, the controller 6 executes aprocessing of outputting from the output circuit 30 a clutch pressurecommand signal for shifting the speed stage to a neutral stage N, i.e.,a command signal for deleting all the contents of the clutch pressurecommand signals C₁ to C₇ regardless of the content of the clutchpressure command signal which has been presently outputted from theoutput circuit 30.

Otherwise, the controller 6 executes a processing of bringing in anengaged state a clutch pressure available for a clutch other than thespecifically identified clutch as mentioned above and then selecting aspeed stage nearest to the speed stage which has been presentlyselected. In other words, in a case where the present speed stageremains at a speed stage F₂ (at which the H/L clutch L and the SP clutch2nd are operable) and the controller 6 specifically identifies as afailure position the SP clutch valve 15 corresponding to the SP clutch2nd, the controller 6 cancels the engagement command which has beenissued to the SP clutch 2nd. Thereafter, the controller 6 executes aprocessing of allowing a clutch pressure command signal to be outputtedfrom the output circuit 30 so as to select a speed stage F₁ (at whichthe H/L clutch L and the SP clutch 1st are operable) which does notrequire that the SP clutch 2nd nearest to the speed stage F₂ is broughtin an engaged state.

(2) In a case where the controller 6 determines that a failure arises inan electric system, i.e., abnormality is present with respect to theclutch pressure sensors 19 to 25 (corresponding to the determinations asdescribed in the paragraphs (4), (6), (10) and (12)) or the controller 6determines that abnormality is present with respect to the input shaftrotation sensor 9 or the output shaft rotation sensor 11 (correspondingto determinations at the paragraphs (1) and (7)), since no problemappears even through running of the engine continues further while thepresent speed stage is unchangeably maintained, the controller 6 outputsfrom the output circuit 30 the content of the clutch pressure commandsignal which has been presently outputted from the output circuit 30 asit is (step 115).

As is apparent from the above description, according to the embodimentof the present invention, the controller 6 determines whether or not theH/L clutches and the SP clutches are properly brought in an engagedstate in conformity with the clutch pressure commands. In addition, thecontroller 6 determines whether or not the H/L clutches and the SPclutches are properly selected and then brought in an engaged state andthe respective shafts located before and behind the H/L clutches and theSP clutches are rotated in conformity with the speed reduction ratioscorresponding to the H/L clutches and the SP clutches which have beenselected in that way. At this time, the controller 6 exactlyspecifically identifies based on the results derived from theaforementioned determinations the position in the speed changing systemwhere a failure arises in an electrical system (signal system) or amechanical system (hydraulic system).

In connection with the aforementioned points, since the conventionalapparatus is constructed such that the controller generally specificallyidentifies the position where a failure arises on the assumption that atransmission shifting valve is properly actuated in conformity with aclutch pressure command so that a speed changing clutch is properlybrought in an engaged state, it has drawbacks that it is short ofaccuracy and it is inferior in respect of reliability. In contrast withthe conventional apparatus, the apparatus in accordance with theembodiment of the present invention has an advantageous effect that itsreliability is improved substantially.

In addition, since any failed part in the apparatus is quickly repairedin response to an information on the position where a failure hasarisen, other advantageous effect of the present invention is that aperformance of serviecs to be rendered for the apparatus is improvedremarkably.

Additionally, since it is possible that the apparatus continues runningof the engine further while the present speed stage is unchangeablymaintained or it is shifted to another available speed stage when thecontroller determines based on an information on the failure positionthat there is few possibility that a movement machine or a constructionmachine is exposed to danger, another advantageous effect of the presentinvention is that an operational effect of the movement machine or theconstruction machine is improved remarkably.

The present invention has been described above with respect to theembodiment wherein it is presumed that a speed changing system forselecting a speed stage by combining the H/L clutches with the SPclutches arranged in the two-staged speed changing unit is employed forthe apparatus of the present invention. However, it should of course beunderstood that the present invention should not be limited only to thisembodiment. The present invention may equally be applied to a system inwhich a speed changing operation is performed with the aid of asingle-staged speed changing unit or a speed changing unit having threeor more stages.

In addition, the present invention has been described above with respectto the embodiment wherein it is presumed that a controlling operation isperformed such that the H/L clutches and the SP clutches (speed changingclutches) are released from their engaged state by actuating hydraulicunits. However, the present invention should not be limited only to thisembodiment. Alternatively, the present invention may equally be appliedto a case where a controlling operation is performed by actuatingpneumatic units or a case where various types of speed changing clutchessuch as mechanical type clutches are employed for the apparatus.

According to the embodiment of the present invention, the controllerdetects with the aid of pressure sensors whether the respective speedchanging clutches are brought in an engaged state or not. Alternatively,the present invention, of course, may be carried out by employingdisplacement sensors, load cells or similar sensors, provided that it isproven that they can detect whether the respective speed changingclutches are brought in an engaged state or not.

It should be noted that the present invention, of course, be applied notonly to an automatic speed changing system in which an optimum speedchanging stage is selected by selecting one of speed stage ranges (e.g.,R, N, 3, 2, 1) (wherein an optimum speed stage is selected among fromspeed stages F₂ to F₈ when e.g., the speed stage range 3 is selectedfrom the foregoing speed stage ranges) but also a manual speed changingsystem in which one of the speed stages is determined in accordance withan operator's intention.

Additionally, the present invention has been described above withrespect to the embodiment wherein a processing of maintaining a speedstage based on the result derived from the determination on the positionwhere a failure arises is executed automatically. However, the presentinvention should not be limited only to this embodiment. Alternatively,the present invention, of course, be carried out by adequatelyneglecting processings to be executed automatically. Further, thepresent invention may be carried out by manually executing theaforementioned processings (operator's actuations) in such a manner thatthe results derived from determinations can be indicated on a displaydevice which is constructed by a cathode ray tube, a liquid crystal andothers.

As described above, according to the present invention, since theapparatus assures that the position where abnormality arises in thespeed changing system can specifically be identified with excellentaccuracy, reliability of the apparatus, a performance of services to berendered for a vehicle or the like having the apparatus installedthereon and an operational efficiency of the vehicle can be improvedsubstantially.

INDUSTRIAL APPLICABILITY

As is readily apparent from the above description, the apparatus fordetecting abnormality in a speed changing system in accordance with thepresent invention is preferably employable for a vehicle such as aconstruction machine or the like including a speed changing system,since the position where abnormality arises can specifically beidentified with excellent accuracy using the apparatus of the presentinvention.

We claim:
 1. An apparatus for detecting abnormality in a speed changingsystem including a transmission composed of a plurality of speedchanging clutches to perform a speed changing operation in response to aspeed stage command so as to select one of said speed changing clutchesand then bring them in an engaged state, characterized in that saidapparatus comprises;clutch engaged state detecting means arrangedindependently of said speed changing clutches to detect whether saidspeed changing clutch is brought in an- engaged state or not, rotationalspeed detecting means for detecting a rotational speed of each of shaftslocated before and behind said speed changing clutches, clutch engagedstate determining means for determining based on the content of saidspeed stage command in response to an output from said clutch engagedstate detecting means with respect to each of said speed changingclutches whether or not said speed changing clutch is brought in anengaged state in conformity with the content of said speed stagecommand, rotational speed determining means for determining based on thecontent of said speed stage command in response to an output from saidrotational speed detecting means whether or not one of said shaftslocated before and behind said speed changing clutches is rotated at aspeed reduction ratio corresponding to said speed changing clutch whichhas been selected and then brought in an engaged state in conformitywith the content of said speed stage command, and means for detectingbased on the results derived from the determinations of said clutchengaged state determining means and said rotational speed determiningmeans the position where said abnormality has arisen in said speedchanging system.
 2. An apparatus for detecting abnormality in a speedchanging system as claimed in claim 1, characterized in that saidtransmission includes an auxiliary speed changing clutch located at afirst stage as seen from an input shaft of said transmission and a mainspeed changing clutch located at a second stage as seen from the same,and that said speed changing system is a system for performing a speedchanging operation in response to said speed stage command while saidauxiliary speed changing clutch is combined with said main speedchanging clutch.
 3. An apparatus for detecting abnormality in a speedchanging system as claimed in claim 2, characterized in that saidrotational speed detecting means serves to detect a rotational speed ofsaid input shaft of said transmission, a rotational speed of anintermediate shaft disposed between said auxiliary speed changing clutchand said main speed changing clutch and a rotational speed of an outputshaft of said transmission.